Skip to content
Case study

Ocean Marina Wall Weathers Massive Storms

06 September 2019

Redi-Rock® reinforced wall withstands significant tidal fluctuations

Ocean Marina Wall Weathers Massive Storms
Finished Wall with bridge at Rhyl Harbour

Marine wall weathers tidal fluctuations and storms

Redi-Rock precast modular blocks provide more cost-efficient solution than sheet piles.

With the goal of increasing tourism and boosting the local economy, officials needed a solution that would stand the test of time, as well as stand out aesthetically, for the major infrastructure improvements to Rhyl’s riverfront area.

The overall breadth of the project along the Irish Sea at the mouth of the River Clwyd included a new public square, a sustainable pedestrian/cycle bridge that would be part of the Wales Coast Path, deepening of the channel to improve navigation, extending the quay, as well as coastal erosion and flood protection.

Finding a cost-effective solution for the quay

Conventional sheet piles were considered for the retaining walls needed for the quay, but they were deemed too cost-prohibitive. Officials turned to local Redi-Rock manufacturer CPM Group to help design a solution using massive, precast modular blocks.

With the assistance of Groundsolve Ltd Geotechnical Consultants, CPM Group designed a 188m (617ft) long, 7.4m (24.3ft) tall quay wall using Redi-Rock Positive Connection (PC) blocks in the limestone texture.

Unlike mechanically stabilised earth wall systems that rely on a friction connection for the geogrid, PC blocks use a 300mm (12in) wide strip of geogrid that wraps through a core slot in the 689kg (1,518lb) blocks. There’s virtually no chance of a connection failure; and, the system is corrosion-free, so it’s ideal for water applications.

Designed for changing tides and extreme weather

Designers factored in the rough coastal conditions at Foryd Harbour, modelling the wall based on the 100-year extreme water level from the Environment Agency. A lag of 2m (6.6ft) was assumed in the design to model the tide going out, and the Redi-Rock blocks were installed on a concrete foundation.

An underwater grout was used to fix the blocks in position, and to prevent scour 3 to 4m (9.8 to 13.1ft) long steel sheet piles were installed in front of the wall. Concrete was poured in the void between the back of the sheet piles and the block face.

The 16-courses of Redi-Rock blocks are reinforced using Miragrid 10 XT, 20 XT and 24 XT geogrid strips, and a reinforced concrete coping was cast on-site, which tied the top course of blocks to the lower course and also created a beam along the wall.

To learn more about the project and how the wall performed during a massive storm, view the full case study at

This is a paid-for/sponsored case-study

  • Robbie Maddison, knowledge content producer at ICE